A wavelength division multiplexer (WDM) is used to merge lights with different wavelengths for transmission on the same optical fiber, or split lights with different wavelengths for transmission on separate optical fibers. The device is widely used in fiber optic communication networks, bi-directional transmission and CATV systems.
FIG. 1 of the attached drawings shows a thin-film filter WDM, comprising optical fibers 111, 112, 113, a dual-core collimator 121, a single-core collimator 122, and a thin-film filter 130. The thin-film filter WDM has the advantages of good optical characteristics, and high stability. However, it also has the disadvantages of requiring active alignment for assembly, and using expensive components, such as collimators.
FIG. 2 shows a fused-type WDM manufactured with the fused biconic taper technology to fuse the optical fibers 211, 212, 213 to form a WDM 220. The fused-type WDM has a low production cost. However, it also has the disadvantages of having poor optical characteristics, such as narrow pass bandwidth, and low wavelength isolation. It is important to find a method to manufacture a WDM with good optical characteristics at a low production cost.